The present invention relates to clutch mechanisms for selectively transmitting power from a drive shaft to a driven shaft, and particularly to a cone-type clutch having a cone-shaped housing coupled to a drive shaft for engaging a cone-shaped friction cone coupled to a driven shaft to establish a driving connection between the shafts. More particularly, the invention relates to a cone clutch that is activated by rotating two actuating levers relative to each other to engage opposing ramp surfaces and separate the actuating levers axially in order to force contact between the cone-shaped housing and friction cone.
Clutches for use with engine-driven machines, such as self-propelled lawn mowers, are known. Typically, an operator stands behind a self-propelled lawn mower and moves a shift lever to engage a clutch mechanism to transmit power from the lawn mower engine to the lawn mower drive wheels. For example, lawn mower clutches are disclosed in U.S. Pat. Nos. 4,205,509; 3,289,800; and 3,270,842. Cone clutches are disclosed in U.S. Pat. Nos. 4,212,379; 4,189,038; and 203,308. A friction clutch is disclosed in U.S. Pat. No. 430,097 to Watson.
Unfortunately, most conventional clutches of the type provided on lawn mowers are either fully engaged to turn the drive wheels or fully disengaged to disconnect the rotating drive shaft and the wheels. Movement of the shift lever by the operator causes the clutch to move either into, or out of, engagement without any partial engagement. This action can cause the lawn mower to "lurch" forward whenever the clutch is engaged. Many operators are unsatisfied with lawn mowers that tend to lurch forward when the clutch is engaged. A clutch mechanism that would permit an operator to engage the clutch gradually using the shift lever would be well-received by consumers and would be a substantial improvement over conventional clutches.
According to the present invention, a clutch assembly is provided for transmitting power from a drive shaft to a driven mechanism. The clutch assembly includes an assembly shaft coupled to the drive shaft, output means for transmitting power, and means for coupling the assembly shaft to the output means. The coupling means includes a first member that is coupled to the assembly shaft for axial movement relative to the assembly shaft and a second member movably coupled to the assembly shaft for axial and rotational movement relative to the assembly shaft.
In preferred embodiments, the first member of the coupling means includes a cone housing mounted on the assembly shaft for axial movement along the assembly shaft during actuation of the clutch assembly. The output means includes a sprocket coupled to an outer end of the assembly shaft and arranged so that the cone housing lies between the drive shaft and the cone housing. The second member of the coupling means includes a friction cone coupled to the sprocket and oriented to move toward and engage the clutch housing during actuation of the clutch assembly.
The cone housing includes an annular sleeve portion engaging the assembly shaft and a frusto-conical portion having an axially outwardly opening aperture sized to receive the cone-shaped friction cone therein. Means is provided for locking the cone housing to the assembly shaft to block rotation of the cone housing relative to the assembly shaft while allowing axial relative movement between the cone housing and the assembly shaft during actuation of the clutch assembly.
A pair of rotatable actuating levers is used to provide means for moving the cone housing into engagement with the friction cone. Each actuating lever includes a lever arm, a central hub, triangular tabs, rectangular tabs, and an annular thrust bearing. Each central hub is formed to include a central opening receiving the annular sleeve portion of the cone housing therein so that the lever arms are pivotable about the longitudinally extending axis of the cone housing. The triangular tabs are formed on the central hub so as to project orthogonally to the central hub and parallel to the longitudinal axis of the assembly shaft. The rectangular tabs are formed on the central hub so as to extend parallel to the longitudinal axis of the assembly shaft and away from the triangular tabs. The rectangular tabs are sized and positioned to retain the annular thrust bearing in place adjacent the central hub.
The actuating levers are mounted for pivoting movement on the cone housing and arranged so as to position the central hubs adjacent each other and between the thrust bearings. The triangular tabs on one actuating lever are arranged to lie in direct opposing relationship to the triangular tabs on the other actuating lever. The actuating levers are arranged on the annular sleeve portion of the cone housing so as to position the cone housing between the actuating levers and the friction cone with the axially outwardly opening aperture of the cone housing opening toward the friction cone.
When the actuating levers are moved relative to one another, the opposing triangular tabs on the actuating levers will cam on each other and cause the actuating levers to separate gradually. As the actuating levers separate and thereby moving in axially opposite directions along the longitudinal axis of the assembly shaft, the cone housing is pushed in an axially outward direction into engagement with the friction cone by the camming action of the triangular tabs. This outward movement of the cone housing causes the friction cone and cone housing to engage gradually and transmit power from the drive shaft to the sprocket and, in turn to drive wheels of the lawn mower. Thus, the camming action of the triangular tabs provides for a gradual engagement of a drive mechanism, and thereby provides a substantial improvement over conventional lawn mower clutch assemblies.